I played some guy who was a real challenge. He is a solid 3.5 player with the following characteristics. Both his forehand and his backhand are mostly flat and are consistent but not very powerful and he doesn't go for much with them. When I'm back at the baseline he often hits some low slice shots. If I come up to the net he can hit passing shots from both sides and will often hit effective lobs as well. When I hit aggressive shots he seems to be able to retrieve everything and just lobs them back. This was weird because I lost this match against a defensive player yet I didn't hit very many unforced errors. It seemed like his lobs, passing shots, and his short slice shots when I was back deep really won the match. He seemed unbeatable, yet he has lost to some other 3.5s that I have beaten or am capable of beating. How can I beat this guy?